298 



Leech and Chandler: Coleoptera 



14. All tarsi apparently 4-segmented (1st segment reduced 

 to a minute nodule); small, squat beetles, head usually 

 deflexed, in contact with front coxae, not visible 

 from above GEORYSSIDAE 



— At least 1 pair of tarsi with more than 4 segments, 

 and other characters not as above . . HYDROPHILIDAE 



15. Elytra truncate, strongly abbreviated, wings usually 

 present and capable of being folded up beneath them; 

 more than 2 tergites and usually the greater part of 

 dorsal surface of abdomen exposed, segments entirely 

 chitinized (fig. 13:43a) STAPHYLINIDAE 



— Elytra usually covering entire abdomen or exposing 

 1 or at most 2 segments; if elytra much abbreviated, 

 the beetles are truly apterous and have extensile 

 membranous vesicles (fig. 13:44a) on prothorax and 

 between metathorax and abdomen 16 



16. Antennae short, more or less geniculate, last 3 seg- 

 ments forming a compact club with segmentation in- 

 distinct; middle and hind coxae widely separated on 

 median line; front tibiae dentate externally; elytra 

 truncate, exposing 2 abdominal tergites which form a 

 pygidium HISTERIDAE 



— Not having above combination of characters 17 



17. Head beyond eyes produced into a distinct beak, on 

 the end of which are the mandibles and trophi 



CURCULIONIDAE 



— Head not prolonged into a distinct beak 18 



18. All tarsi actually 5-segmented, but segment 4 very 

 small and nearly concealed within lobes of 3 (fig. 

 13:60c); first 3 segments dilated, with adhesive (hairy) 

 pads beneath; beetles of from 5 to 10 mm. in length 



CHRYSOMELIDAE 



— Tarsi with 5 or fewer segments, but not fitting above 

 description 19 



19. Head with 2 dorsal ocelli, near mid-line and behind 

 an imaginary line across hind margin of compound 

 eyes; antennae filiform, tarsi 5-segmented, elytra 

 polished, glabrous except for lines of long, nearly 

 erect setae BRATHINIDAE 



— Head lacking ocelli 20 



20. Hind coxa with projection covering base of trochanter, 

 this projection sometimes extended laterally along 

 coxa to form a groove into which anterior margin of 

 trochanter and femur fit when retracted 21 



— Hind coxa without a projection covering base of 

 trochanter, anterior margin of femur never fitting into 

 a groove in coxa 27 



21. Front coxae more or less conically projecting; hind 

 margin of pronotum never crenulate (fig. 13:47e) . .. 



HELODIDAE 



— Front coxae variously formed; if projecting, then hind 

 margin of pronotum is crenulate 22 



22. Front coxae more or less exerted and projecting, 

 and/or hind margin of pronotum crenulate 23 



— Front coxae transverse or rounded 24 



23. Mandibles concealed when closed; labrum usually 

 invisible or nearly so from in front; head usually 

 slightly rostrate, because of clypeus projecting from 

 between somewhat approximated antennal insertions 

 (fig. 13:58c) . .• PSEPHENIDAE 



— Mandibles always partly visible, frequently conspicu- 

 ous; labrium nearly always in full view from in front; 

 head not at all rostrate PTILODACTYLIDAE 



24. Tarsi 4-segmented, last segment shorter than rest, 

 claws slender; front and middle tibiae broad and 

 spinose along their outer edges; antennae short, much 

 thickened HETEROCERIDAE 



— Tarsi almost always 5-segmented, last segment usually 

 as long as rest together, claws usually large and 

 strong; front and middle tibiae narrow, not spinose; 

 antennae often filiform 25 



25. Middle coxae widely separated, hind coxae nearly 

 or quite contiguous; legs retractile, last segment 



of tarsi shorter than rest together (fig. 13:57a) 



LIMNICHIDAE 



— If middle coxae are separated, hind coxae are equally 



so; legs not retractile, last segment of tarsi usually 

 as long as rest together, claws large 26 



26. Antennae very short, 6 or more apical segments form- 

 ing a close pectinate club; female genitalia without 

 styli, usually asymmetrical (fig. 13:49a) 



DRYOPIDAE 



— Antennae usually slender, never with apical segments 

 forming a close pectinate club; female genitalia 

 symmetrical, with movable styli (fig. 13:54c) 



ELMIDAE 



27. Tarsi all 5-segmented; elytra abbreviated, wings com- 

 pletely absent; body with extensile membranous 

 vesicles on prothorax and between metathorax and 

 abdomen (fig. 13:44) MELYRIDAE 



— Hind tarsi 4-segmented; elytra not abbreviated; body 

 without extensile vesicles 28 



28. First 3 visible abdominal sternites connate; eyes 

 transverse and emarginate TENE3RIOXIDAE 



— All visible abdominal sternites similar and movably 

 articulated to each other; eyes rounded, not emarginate 



28 



29. All coxae widely separated on median line; slow- 

 moving species occurring in cracks of rocks in the 

 intertidal zone EURYSTETHIDAE 



— Front and middle coxae nearly or quite contiguous 

 on median line; active species, often near margins 

 of streams or alkali lakes ANTHICIDAE 



Key to Nearctlc Families of Aquatic 



and Semlaquatic Coleoptera 



Larvae 



1 . With legs 2 



— Without legs 28 



2. Legs apparently 5-segmented, tarsi with 2 movable 

 claws (except Haliplidae which are 1-clawed). Sub- 

 order ADEPHAGA 3 



— Legs apparently 4-segmented, tarsi united with a 

 single claw. Suborder POLYPHAGA 9 



3. Tenth abdominal segment armed with 4 hooks; spir- 

 acles absent; lateral gills present on all abdominal 

 segments; cardo very large; (fig. 13:21). GYRINOIDEA 



GYRINIDAE 



— Tenth segment not armed with 4 hooks; spiracles 

 usually present; with or without lateral gills; cardo 

 of moderate to small size. CARABOIDEA 4 



4. Abdomen 9-10 segmented 5 



— Abdomen with 8 visible segments 7 



5. Tarsi 1-clawed; abdomen 9-10 segmented (fig. 13:5) 



HALIPLIDAE 



— Tarsi 2-clawed; abdomen 9 segmented 6 



6. Terminal tarsal setae much shorter than claws; re- 

 tinaculum single or absent; littoral in part 



CARABIDAE 



— Terminal setae much longer than claws; retinaculum 

 / bicuspidate; littoral OMOPHRONIDAE 



^7. Legs fossorial, larval form elaterid (wireworm) like 

 (fig. 13:19a), mandible with distinct retinaculum, 



inner margin neither sulcate nor tubular 



NOTERIDAE 



— Legs ambulatory or natatory, larval form not elaterid- 

 like; mandible without distinct retinaculum, inner 

 margin either sulcate or tubular 8 



8. Larvae flattened, thoracic and abdominal sides greatly 

 expanded into thin lateral plates; cerci 1-segmented, 

 thick, blunt at tips; gular suture median and simple 

 (fig. 13:2) AMPHIZOIDAE 



— Larvae not with sides greatly extended; gular suture 

 double , at least anteriorly (fig. 13 : 12a, b) 



DYTISCDDAE 



9. Urogomphi (cerci) segmented or individually movable 

 (often retracted into a terminal breathing pocket in 

 8th abdominal segment in Hydrophilidae) 10 



